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Discussion Starter #1
Anyone on here good with diesels? I'm helping a friend with a boat that is making a taping/ knocking noise (doesn't really sound that deep though). First I thought it was an injector, so I swapped #1 with #6. , noise still there!, If you disconnect #1 injector noise goes away!. Valves are all adjusted perfect. If I put a long screwdriver to my ear and to engine block it isnt very noticable, put it to cylinder head or head bolt not very noticable, put it to the #1 injector fuel line and it is as loud as can be! ?????? WTF it's not the injector? the damn fuel line goes into a common fuel rail? very strange. I am guessing maybe cracked piston or hole in piston? :smt017
 

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My knocking noise that came and went was actully the pieces of ring that ended up on top of the piston, yes major blow by issue as well, this appears to be common on number 6 though! It was quiet when cold but when hot the ring would break loose on the top of the piston until it got hammered into the piston in it's new spot! Not pretty ended up needing a sleeve for number 6!
 

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Wrist pin bushing or valve seat fell out. Had to say without hearing it.
 

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Does the noise sound like it is at crank rpm( then piston) or at 1/2 rpm ( then can be valve train or cylinder firing). Dont take this at gospel but may help get you looking in the right direction. Don't over think it, it's an engine.
 

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Discussion Starter #7 (Edited)
sounds like crank rpm (we tried counting taps in a minute, came up with around 120 and engine was running around 700rpm) , oil PSI is normal cold and hot, noise is when cold as well as hot. It does get a little quieter sometimes but not very long. It is loud at idle and when rpm is raised. I'm gonna bore scope it today or tomorrow to see if I can find something. Just want to make sure before tearing down! As long as block doesn't have to come out we will be good! I can't imagine how the fuck they get an engine out of one of these boats! This is the port side engine but the stairs going up are on the starboard side! plus everything is badass veneer wood finishes, off white carpet, areas wrapped in leather, etc. looks real easy to mess things up!! Also found out these motors are a little different than a common 5.9. Blocks are different, internals, etc. thing is factory rated 450HP each.

Thanks for input
 

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Try another injector before yo go ripping the engine apart. Buddy put rebuilt injectors on his GM diesel many years ago. One was bad out of the box and you would have sworn it was a rod bearing knocking. Old mechanic at the dealer I worked for tipped us off.
 

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Discussion Starter #10
I swapped #6 and #1 injector and the noise never changed? Also swapped the fuel tube thing as well? (piece that goes from fuel line into head into injector) (still coming from #1 cylinder) It is not the injector but when I disconnect #1 injector the noise goes away. I'm thinking it has to be piston or pin? hopefully borescope will see something. Of course it will be pin or cracked piston on the bottom side so I won't see shit with scope. Just very weird the sound is loudest when you put screwdriver from your ear onto #1 fuel line! Can an injector pump make that sound? never mind it wouldnt go away when injector disconnected... thinking out loud. lol
 

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fuel can do some goofy things , when i was at cummins we had an isx with a hard knock pulled pistons , nothing wrong , thought it might be oil pump , nope , turned out to be a fuel actuator , i know different animal , but fuel is wierd .

id pull oil filter and check for metal , its quick and easy to tell if its bottom end .

also , on some of these newer motors , i think 07 and up injectors are cylinder specific , meaning you cant put a 6 on 1 . they must go to there dedicated cyl ,
 
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